TSi Dynamics is a Mathematica package containing functions that support the assembly of mathematical models and simulation models for mechanical systems. In its current form, TSi Dynamics accommodates tree structures composed of combinations of rigid and flexible bodies and simple and compound kinematic joints, and which may also have supplemental algebraic and/or differential constraints. Thus, systems with closed loops and nonholonomic joints can be treated.

TSi Dynamics creates fully nonlinear, explicit models. The model building process requires that the user provide defining data for individual joints and bodies, as well as the system interconnection structure. The joints are defined in terms of their primitive action parameters from which all the required kinematic relations are derived. Thus, a user can contrive unusual joint configurations and is not restricted to a predefined set of standard joints. The equations are formulated in Poincar's form of Lagrange's equations that admits the standard Lagrange equations as a special case. However, Poincar's form allows the exploitation of quasi-velocities which can significantly simplify the equations of motion.

TSi Dynamics assembles the equations of motion and it contains functions that facilitate simulation. Simulation may done within Mathematica or externally using some other simulation software. TSi Dynamics includes functions which assist in performing simulations using the NDSolve function in Mathematica and other functions to construct a C-code subroutine that compiles as a "MEX-file" for use with MATLAB/SIMULINK.